Shortening A Drill Chuck

having had a chinese drill chuck with pretty poor run out (>15thou), I would personally look into buying a decent condition used Jacobs off ebay with a 3/4in arbor already attached. Or any decent drill chuck and a separate 3/4in arbor. I agree that it's great to save money and use what you have, but this is a fair amount of work on something that might not warrant it. Before doing anything I'd first check, if possible, how much run out the chuck has over its clamping range. If it's anything more than a few thou, I'd sling it in the "might use one day" box and get a better one.
 
O.K. Here's the follow up on the Chinese drill chuck, (and a side note to Mattthemuppett...I own a few Jacobs chucks). I used my ETM collet chuck and inserted a 1/2" dowel pin in it and checked the run out... Perfect"0", I then clamped the chuck jaws onto the pin and checked the run out...back to four grand, at the chuck end, BUT... the threaded end for the drawbar was wobbling perhaps forty-five grand...ROFLMAO!
Since I could not use a center in the end, I snuck up on it five thou at a time so I wouldn't have too much of a side load (right Bob?). I took the shaft down to .8750 and sawed off the rest. I clamped it back onto the dowel pin and faced off the end and indicated it in. WOW the indicator is broke...OR, it's not moving. I center drilled the end, cleaned up and ran it in the mill. With a 1/2" dowel pin, my test indicator reads within 0.0002!
I'll buy that!
It just totally amazed me the total run out [TIR] from the factory! Now I have a decent chuck within tolerance to use for short work on the mill. I am hoping that some of the newer members coming in will follow along and save their "questionable" tools too
A big....THANKS FOR THE INPUT,
Toolroom
 
good for you. Now chuck it up and try a 3/8, 1/4 and 1/8 dowel pin :)

No axe to grind here, but similarly I wouldn't want some of the newer members to get the impression that all chinese drill chucks are dead nuts tenth reading precision instruments..
 
True, and I agree Matt and John. I have had this Chinese chuck for twenty years and never used it. After close inspection...I can see why. Just thought it would be a good idea to try and salvage it. I have a 3/8 dowel pin, Matt but will go to ACE hardware to purchase the others. It would be cool to see if the jaw gully's are ground correct.
The point of the project was to ask about the mounting procedure to turn the shank, and it WAS really neat to see that all who responded were all on the same thought wave, about keeping in line with the axis!
toolroom
 
O.K., Mattthemuppet...Here we are with new readings from the different size hardened dowel pins. I did this on both my Chinese chuck that I shortened AND my Jet drill press. Just for kicks I will call the Chinese chuck "C" and the Jet "J".
1/2" dowel C=.0002 J=.012, 3/8"dowel C=.0006 J= .002, 1/4" dowel C .001 J= 003, 1/8" dowel C=.0025+ J=.007
I logged onto the Jacobs chuck site and checked their run out, and found that Jacobs uses the 1/2 capacity as a mean. .004is their acceptable tolerance on plain bearing medium duty chucks.
So, taking the mean between these two chucks, I am C=(approx. .0023, I'll call that within. The Jet=.005 TIR (nfg) out of acceptable tolerance.
I think, that through all involved here, what permissible run out is, and what we all may have in our drill chucks, thanks to matt the muppet for bringing this to (my) our attention.
Hats off to Matt
toolroom
 
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